The antioxidant effects of cerium oxide nanoparticles (CNPs) on semen after chilling (at 4°C for 72 hrs) storage were evaluated in New Zealand White rabbit bucks. Semen was collected from ten bucks (1–1.5 years old), diluted in Tris extender, and supplemented with CNPs at 0, 20, 40, 60, and 80µg/mL. Sperm motility, livability, abnormality, and membrane integrity were evaluated at 2, 24, 48 and 72 hrs of cooled storage. Additionally, the concentrations of malondialdehyde (MDA) and protein carbonyl (PCO), along with the activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and total antioxidant capacity (TAC), were assessed after 72 hours of chilling. The attained findings showed that 40 and 60 μg CNPs/mL provoked the most beneficial effects on sperm motility, livability, membrane integrity, and normality. The 60 μg/mL concentration was the most effective, enhancing sperm motility by 4.58, 13.74, 26.98, and 50.33% after 2, 24, 48, and 72 hours, respectively, compared with the control. Sperm viability increased by 5.94, 12.08, 32.30, and 60.67% at the same time points. Membrane integrity improved by 4.68, 12.35, 23.18, and 28.91% at the same intervals. Moreover, sperm normality showed a consistent improvement of approximately 26% across all cooling intervals. However, 80 μg CNPs /mL had negative effects. The 60 µg/mL dose also improved antioxidant markers after 72 h (P<0.001). Collectively, adding 60 µg/mL of CNPs to Tris semen extender resulted in significant enhancements in the NZWB semen characteristics after up to 72 hrs of cooling at 4°C.